1. Technical Field
The present invention in general relates to a storage system and its management method, and in particular relates to technology for managing the attributes of volumes in each of the plurality of storage apparatuses configuring the storage system.
2. Description of the Related Art
In order to prevent the loss of data due to a failure of a storage apparatus in a computer system, data stored in a certain logical volume in the storage apparatus is normally backed up in a logical volume of physically different storage apparatus configured redundantly. For example, remote copy (or remote mirroring) is known as a type of technology for backing up data. Specifically, remote copy defines a logical volumes (active volume) in an active storage apparatus and a logical volume (standby volume) in a standby storage apparatus as the remote copy pair volumes, and synchronously or asynchronously duplicates data in the active volume to the standby volume to back up data. By way of this, even if a failure occurs in the active storage apparatus, the standby storage apparatus can succeed the I/O access request from the application of the host computer.
With a large-scale computer system, demanded is a “nondisruptive operation” of switching the storage apparatus (or the logical volume therein) without disrupting the execution of applications of the host computer. Thus, even when disrupting the active storage apparatus for reasons other than failure such as for maintenance work, the host computer is required to immediately switch to the standby storage apparatus in a state where the applications are in nondisruptive operation.
In order to achieve this kind of nondisruptive operation, a technology has been proposed for equipping the host computer with an alternate path module and selectively switching the I/O access path to the storage apparatus with a pair relationship defined therein.
For example, Japanese Patent Laid-Open Publication No. 2006-11874 (Patent Document 1) discloses a technique of selectively switching the storage apparatus to which the host computer is trying to I/O access without disrupting the applications. Specifically, Patent Document 1 discloses a volume filter program used for causing a target program (OS, application program, etc.) of the host computer to recognize either one of a copy source volume and a copy destination volume configuring a volume pair. When the volume filter program, for example, detects a situation where the active copy source volume cannot be used due to failure or maintenance work, the volume filter program automatically switches the I/O access path to the standby copy destination volume.
Such an alternate path module can also be applied, by using the virtual volume function, to a storage system that provides the logical volumes (real volumes) in a physical device as virtual volumes in a plurality of storage controllers to the host computer. The virtual volume function allows a system administrator to allocate applications to a virtual volume without having to be aware of the logical volumes in the physical device, thereby reducing workloads of the system administrator.
Japanese Patent Laid-Open Publication No. H10-283272 (Patent Document 2) discloses a technique that the storage server provides a virtual volume to the host computer. Specifically, Patent Document 2 discloses that the storage server detects the volumes in the respective storage systems, manages such volumes as storage areas that have not yet been allocated to itself, and creates a virtual volume in the storage server based on one or more volumes in the foregoing unallocated storage areas so as to allocate a virtual volume to the host computer. In the I/O access from the host computer to the virtual volume, the storage server sequentially converts the virtual volume into an address of the real volume and relays the I/O access.